1. Field of the Invention
The present invention pertains to an aerosol medication delivery system, and, in particular, to a valved holding chamber for use in an aerosol medication delivery system that maximizes delivery of the aerosol medication to a patient.
2. Description of the Related Art
It is well known to deliver a medication to a patient's respiratory system to treat a medical condition using an aerosol medication delivery system. For example, a patient suffering from an acute asthmatic attack may use an aerosol medication delivery system to deliver a bronchodilator, such as albuterol (salbutamol), in the form of a fine mist to the patient's respiratory system.
A conventional aerosol medication delivery system often consists of a metered dose inhaler (“MDI”) and a spacer. The MDI, also known simply as an “inhaler”, includes a canister or nebulizer that contains the medication under pressure and a canister holder, which is typically “L” shaped. Although it is common for a patient to use the canister holder as a mouthpiece for receiving the aerosolized medication into their airway directly from the aerosol dispensing leg of the canister holder, this configuration may not optimize the mixing of the medication with the air because the aerosolized medication is injected directly into the airway. Without adequate mixing of the drug with the air, the medication may not be inhaled into the patient's lungs where it is effective, but may form as droplets that are deposited in the patient's mouth and swallowed without the desired medicinal effect.
To enhance mixing of the medication with air, it is known to provide a spacer that attaches to the aerosol dispending end of the canister holder. The spacer, which is typically a small hollow cylinder with a one-way valve at the downstream end, receives the aerosol from the canister and allows it to form into a fine mist for inhalation into the airway of the patient. It is also known to provide a mask at the end of the spacer opposite the MDI so that the patient can breath through his or her mouth to receive the medication. Examples of conventional spacers and associated components are shown in U.S. Pat. Nos. 4,470,412; 4,809,692; and 4,832,015 all to Nowacki et al.; U.S. Pat. No. 5,012,803 to Foley et al.; U.S. Pat. No. 5,042,467 to Foley; U.S. Pat. No. 5,385,140 to Smith, U.S. Pat. No. 5,848,599 to Foley et al., and U.S. Pat. No. 6,557,549 to Schmidt et al.
While the spacers described in these patents improve mixing of the medication with air, still further improvements in this mixing is desirable. Furthermore, the devices described in these patents are relatively complicated, especially in the valves used to control the flow of the drug/air mixture and patient exhalation. The more complicated the system, the more prone they are to failure or degradation in performance, for example due to clogging, and the more difficult it is to disassemble, clean, and reassemble the system correctly and quickly.